The present invention relates to improvements in mass transport systems, and to such systems wherein a discrete quantity of material is moved from a first location maintained at a first temperature, to a second location maintained at a different temperature. It relates in particular to systems such as a printing system wherein an image- or color-forming material of slight mass is carried to a second location of higher temperature where it is fused to a receiving medium.
In the field of photocopying or printing, it is known to print by first forming an electrostatic latent image on a photoconductive drum or belt, developing the electrostatic latent image on the drum with a toner, and then transferring the toner to a moving belt which carries the toner past a heat fusing station where the toner is melted and transferred to paper or some other print medium. Systems of this type are shown in U.S. Pat. Nos. 3,893,761; 3,923,392; and 3,947,113. Such a system has been made and marketed commercially.
In the commercial system known to applicant, the primary function of the belt is to provide a transport mechanism to carry the developed toner image to a high temperature fusing and transfer station. The belt is a relatively thick belt, e.g., one or more millimeters thick, that is operated isothermally at a temperature over 100.degree. Celsius which is sufficient to fuse the transported toner. In such a construction, the belt serves to isolate the primary latent-image forming member, which is a photoconductive belt, from the high fusing temperatures; this allows the photoconductive belt to operate with a conventional powdered toner image development technology.
Such construction results in a complex assembly wherein a first image forming and toner transport mechanism is operated at one temperature, and a comparably large transport assembly is maintained at a higher temperature within the machine. The machine requires a significant power input for its heated portion, and is mechanically complex. The transfer of toner between two or more intermediate members adds considerations of image quality.
Accordingly, it would be desirable in systems of this sort to simplify the mechanical structure, reduce the power requirements, and improve the image transfer characteristics.